What is a junior ADU and what are the rules?
A junior ADU is up to 500 sq ft inside the existing single-family home, including an attached garage, with an efficiency kitchen and its own or a shared bathroom. With its own bathroom, no owner has to live on the property (AB 1154, from January 1, 2026). A junior ADU, a conversion and a detached ADU can all be built together on a single-family property.
2. Kinds of ADU
| Kind | What it is | Size | Source / status |
|---|---|---|---|
| Detached ADU | New separate building | Up to 1,200 sq ft. A city must always allow at least 800 sq ft at 16 ft tall with 4 ft side and rear setbacks. | Gov. Code §§ 66314, 66321. Confirmed |
| Attached ADU | Addition attached to the home | Up to 50% of the existing home's floor area or 1,200 sq ft, whichever is less. 800 sq ft is always allowed. | § 66321. Confirmed |
| Conversion | Turn existing space (garage, part of the home, accessory building) into an ADU | Existing space, plus up to 150 sq ft added for entry. | § 66323. Confirmed |
| Junior ADU (JADU) | Inside the existing single-family home, including an attached garage | Up to 500 sq ft. Efficiency kitchen required. Its own bathroom or a shared one. | §§ 66333–66339. Confirmed |
How size is measured (SB 543, from January 1, 2026): every square-foot limit means interior livable space: space for living, sleeping, eating, cooking or sanitation. Wall thickness, garages and decks don't count. Confirmed (LA County DRP memo on SB 543 / AB 1154, December 2025).
Combining (SB 543, from January 1, 2026): on a single-family property you can build a conversion ADU, a JADU and a detached ADU together under the ministerial path (§ 66323). On a multifamily property, converted and detached ADUs can be combined. Confirmed.
5. Owner occupancy and rentals
| Rule | Value | Source / status |
|---|---|---|
| ADU owner occupancy | Not allowed to be required. Permanent since AB 976 (2023) | § 66315. Confirmed |
| JADU owner occupancy | Required only if the JADU shares a bathroom with the main home. With its own bathroom, no owner-occupancy rule, and covenants can't include one. | AB 1154, from January 1, 2026. Confirmed |
| Short-term rentals | ADUs and JADUs rent for more than 30 days. AB 1154 applies this to all JADUs and § 66323 ADUs; the city may apply it to others | AB 1154. Confirmed |
| Selling an ADU separately | Only if the city has opted in under AB 1033 (2023) or the ADU is built by a qualifying nonprofit. Don't tell users they can sell an ADU separately in LA City unless the city has adopted AB 1033. | § 66341. Verify LA City's status |
From ADU rules in Los Angeles, the guide the property report is built from. Every line carries its source and status.